A conventional glow plug is described in German Patent Application No. 38 37 128, in which a ceramic heating apparatus is held by the tip of a cylindrical holder. The ceramic heating apparatus is electrically insulated with respect to the holder. Provided on the end of the cylindrical holder which is opposite to the ceramic heating apparatus is a connector apparatus which makes contact to supply voltage. The ceramic heating apparatus consists of a U-shaped heating segment. The two ends of the U-shaped heating segments each make contact with the connector apparatus. During a preheat operation, a voltage is applied to the ceramic heating apparatus so that a current flows through the ceramic heating segment, specifically from one end of the U-shaped heating segment via the tip on the heating segment in the combustion chamber to the other end of the U-shaped heating segment. Due to of the resistance of the ceramic, the current causes heating of the heating segment so that the latter glows and can ignite the fuel/air mixture.